Curiosities of Science. 



action in about six months, so that 18,000 Ibs. of zinc are con- 

 sumed in a year. There are also about 3600 porcelain cups to 

 contain nitric acid ; it requires 450 Ibs. of acid to charge them 

 once, and the charge is renewed every fortnight, making about 

 12,000 Ibs. of nitric acid in a year. 



TIME LOST IN ELECTKIC MESSAGES. 



Although it may require an hour, or two or three hours, to 

 transmit a telegraphic message to a distant city, yet it is the 

 mechanical adjustment by the sender and receiver which really 

 absorbs this time ; the actual transit is practically instanta- 

 neous, and so it would be from here to the antipodes, so far as 

 the current itself is concerned. 



THE ELECTKIC TELEGRAPH IN ASTEONOMY AND THE 

 DETERMINATION OF LONGITUDE. 



The Electric Telegraph has become an instrument in the 

 hands of the astronomer for determining the difference of lon- 

 gitude between two observatories. Thus in 1854 the difference 

 of longitude between London and Paris was determined within 

 a limit of error which amounted barely to a quarter of a second. 

 The sudden disturbances of the magnetic needle, when freely 

 suspended, which seem to take place simultaneously over whole 

 continents, if not over the whole globe, from some unexplained 

 cause, are pointed out as means by which the differences of lon- 

 gitude between the magnetic observatories may possibly be deter- 

 mined with greater precision than by any yet known method. 



So long ago as 1839 Professor Morse suggested some expe- 

 riments for the determination of Longitudes ; and in June 

 1844 the difference of longitude between Washington and Bal- 

 timore was determined by electric means under his direction. 

 Two persons were stationed at these two towns, with clocks 

 carefully adjusted to the respective spots ; and a telegraphic 

 signal gave the means of comparing the two clocks at a given 

 instant. In 1 847 the relative longitudes of New York, Phila- 

 delphia, and Washington were determined by means of the 

 electric telegraph by Messrs. Keith, Walker, and Loomis. 



NON-INTERFERENCE OF GALVANIC WAVES ON THE SAME WIRE. 



One of the most remarkable facts in the economy of the 

 telegraph is, that the line, when connected with a battery in 

 action, propagates the hydro-galvanic waves in either direction 

 without interference. As several successive syllables of sound 

 may set out in succession from the same place, and be on their 

 way at the same time, to a listener at a distance, so also, where 

 the telegraph-line is long enough, several waves may be on 

 their way from the signal station before the first one reaches 



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